The Field of the Invention
This invention relates to measuring and indicating devices, and more particularly to that class of apparatus utilizing electronic components for the measurement of changes in the value of selected electronic components, displaying same in a visual or audible manner.
In particular, this invention relates to an electrical measuring device in which the change in the physical condition to be observed is applied to vary the reactance or resistance of an element in the measuring circuit. In the past, variable reactances have been arranged in bridge circuits, or used to vary the frequency of an oscillator, in order to obtain an indication of the change in magnitude of the reactance due to the change in the physical condition under observation. Such arrangements have been and are, to a great extent, relatively complicated and uncertain in operation. It is an object of the present invention to provide a simple arrangement which is extremely reliable and free from extraneous input, providing an error free measuring device.
A further object of the present invention is to provide an apparatus which is capable of measuring the change in the magnitude of the reactance which is comparatively unaffected by variations in supply potential.
Another object of the present invention is to provide an apparatus for comparing the relative magnitude of two similar reactances, especially in case wherein one reactance is a standard and the other is responsive to some external force, modifying its magnitude.
A still further object of the present invention is to provide a measuring device which performs its measurement repeatedly, over short periods of time, so as to eliminate drift considerations and the introduction of error thereby.
Yet another object of the present invention is to provide measurement device which utilizes solid state circuitry for switching purposes, thereby eliminating noise, error, delay, and bulk and weight.
A yet further object of the present invention is to provide switching circuit configurations such that only the impedance of the switched similar reactance elements are involved in the measuring technique, thereby eliminating relying upon dissimilar elements, appropriate to one or the other similar impedance elements.
A still further object of the present invention is to provide economically constructed circuit configuration wherein only the similar reactance elements are switched, such that other elements, non-reactive in nature, that are simultaneously switched with the elected similar reactance elements, do not create an error in the measurement of the reactance element in use.
A further object of the present invention is to provide an apparatus which has an output capable of being transmitted along a pair of conductors, containing signal information therealong, reflecting both of the similar impedance elements reactance magnitude, after their sequential use.
Yet another object of the present invention is to provide a frequency measuring device, dependent upon the magnitude of the reactance of similar reactances, whose output reflects alternately the impedance of each of the similar reactance elements, thereby a full range of arithmetic operations to be performed on the output signal.